An air charger may be used to increase the output power of an internal combustion engine by increasing the supply of air or combustible mixture to the cylinders of the engine. Prior air chargers include a compressor or blower which is typically driven by exhaust gases or by a crankshaft of the engine through a mechanical coupling. An air charger driven by exhaust gases, however, requires additional exhaust plumbing to route the exhaust gases to the air charger, and also must be designed to accommodate high temperatures associated with the exhaust gases. Such a design typically includes a costly coolant system to decrease the temperature of the charged air. An air charger mechanically driven by the engine tends to be relatively complex, and its placement is limited to certain locations within the engine compartment. Furthermore, the output air flow from these types of air chargers is typically not controllable unless some form of valving is also provided. Such valving, however, tends to be inefficient and inaccurate.
U.S. Pat. No. 5,638,796 shows an electric air charger for supplying air to the cylinders of an engine. This air charger includes a blower housing having an air inlet and an air outlet which are perpendicular to each other, a centrifugal blower mounted on one end of a shaft, and an electric motor having a rotor mounted on the opposite end of the shaft. Because air flow must be redirected between the air inlet and the air outlet, the air charger is relatively inefficient. Furthermore, the blower and the rotor are remote from each other, which adds to the inefficiency of the air charger and increases manufacturing costs. Finally, because the centrifugal blades are fixedly positioned on the blower, the blades cannot be adjusted during operation to improve efficiency of the air charger.
Accordingly, it is desirable to provide an air charger having improved efficiency and reduced cost.